Specularity-Free Projection onto Nonplanar Surface

Abstract - In projection-based augmented reality, specular reflection may distract the users. This paper demonstrates that the specular reflection can be eliminated by redundantly illuminating the projection surface using multiple overlapping projectors mounted at different locations. Our initial system using two projectors is presented. The system automatically determines the pixels which include specular reflection in one projector, blank the light falling on the pixel and boost the other projector’s output so that the added light is projected onto the pixel consistently.

Concept

Figure 1 shows the concept of our system for eliminating specular reflection. Assuming the projectors are calibrated and the surface geometry is known, projection from two projectors can be exactly overlapped and thus the user feels as if there is only a single projection. In general, two projectors hardly produce specular reflection at the same time at the same point of the projection surface because they are separated at a distance. Therefore, it is possible to make user free from specular reflection by blocking the projection by the projector which produces the specular reflection. For instance, at P1 in Fig. 1, the projection by PROJECTOR 2 is blocked and the user sees the boosted projection by PROJECTOR 1 that does not have specular reflection. The projector which generates specular reflection is easily estimated using surface normal. In Fig. 2., the angle θ is small at the specular region.

Preliminary Results - Elimination of specular reflection on a planar surface.

The projection surface is divided by small patches and each planar patch is independently processed. However, the final projection is almost determined by the right projector because the surface normal is almost same at the whole surface. Leftmost image: original image, left-top image: merged image with only geometric registration (the image texture looms because of specluar reflection), right-top image: merged image with geometric registration and specular elimination, left-bottom image: contribution of the left projector, right-bottom image: contribution of the right projector.

Demo - Elimination of specular reflection on a nonplanar surface.

Publication

1. Hanhoon Park, Moon-Hyun Lee, Sang-Jun Kim, and Jong-Il Park, "Specular Reflection Elimination for Projection-Based Augmented Reality," Proceedings of The Fourth IEEE and ACM International Symposium on Mixed and Augmented Reality (ISMAR) 2005, pp. 194-195, Vienna, Austria, Oct. 2005 [paper link]
1. Hanhoon Park, Moon-Hyun Lee, Sang-Jun Kim, and Jong-Il Park, "Specularity-Free Projection on Nonplanar Surface," Lecture Notes in Computer Science 3767, Advances in Multimedia Information Processing, Proceedings of PCM'05, pp. 606-616, Nov. 2005 [paper link]